MCMCB Pro
A51

A51Early syphilis

Non-billable headerICD-10-CM

A51 is a non-billable header ICD-10-CM code for early syphilis. It cannot be billed on its own: choose one of the more specific child codes below.

Other codes that can never be billed with A51

These codes carry an Excludes1 note pointing at A51. The conflict binds both ways, but ICD-10-CM only writes it down on one side — so you would not find this by reading A51 alone.

  • A52.79Other symptomatic late syphilis
  • L99Other disorders of skin and subcutaneous tissue in diseases classified elsewhere
  • M63Disorders of muscle in diseases classified elsewhere
  • M90Osteopathies in diseases classified elsewhere
  • N77.0Ulceration of vulva in diseases classified elsewhere
  • N77.1Vaginitis, vulvitis and vulvovaginitis in diseases classified elsewhere
  • H20.0Acute and subacute iridocyclitis
  • K77Liver disorders in diseases classified elsewhere

Risk adjustment

A51 does not map to an HCC and does not risk-adjust under CMS-HCC V28. That is normal — most ICD-10 codes do not. It still needs to be coded correctly; it just will not move a RAF score.

Code to one of these instead A51

7 child codes. Green means billable.

Questions about A51

Is A51 a billable ICD-10-CM code?
No. A51 is a non-billable header code. Code to a higher level of specificity using one of its child codes.
Where does A51 sit in the tabular list?
Certain infectious and parasitic diseases (A00-B99), in the block Infections with a predominantly sexual mode of transmission (A50-A64).
ICD-10-CMFY2026-Apr· effective April 1, 2026

Loaded directly from the CMS/NCHS ICD-10-CM public-domain release — see data sources and our editorial policy. If this page disagrees with the CMS tabular list, this page is wrong. Reference information for professional coders; not medical or billing advice.